This invention relates to radiant electric heaters such as used in cooktops on stoves, and more particularly, to an advanced radiant electric heater which is lower in cost and has a potentially longer service life than conventional radiant electric heaters.
Radiant electric heating units, as is well-known in the art, comprise an electrical heating element such as a coil heating element, or a ribbon heating element. In conventional heating units, the ends of the heating element connect through a thermal switch to an electrical circuit by which current is supplied to the heating element. The unit is installed beneath a heating surface upon which utensils are placed. Heat generated by the heating element is transferred to the heating surface by radiation, and from the heating surface to the utensil by conduction. The thermal switch is responsive to the heating unit temperature exceeding a preset temperature to open the circuit path between a power source and the heating element to cut off current flow to the heating element. When the temperature falls back below the preset temperature, the switch reconnects the circuit path to restore the current flow to the heating element.
There are a number of problems with existing heating units. One of these is the thermal switch. The thermal switch assembly is expensive, representing 20-30% of the total cost of a heating unit. The switch assembly is a primary source of heating unit failure. It is simply too expensive to replace a failed switch. Rather, when the switch fails, the heating unit is discarded and a new heating unit substituted in its place. Elimination of the existing thermal switch would not only be a substantial cost savings, but would also improve the service life of a heating unit; provided, that proper temperature control of the heating unit is still maintained.
Among the several objects of the present invention may be noted the provision of an improved radiant electric heating unit for use in stoves, cook tops, and the like;
the provision of such a heating unit to eliminate a thermal switch normally used in such units but which is the most expensive item in the unit and one the major sources of heating unit failure;
the provision of such a heating unit to employ a thermal sensing element which is a low cost, reliable element that supplies a temperature indication of the heating unit temperature to a controller or the like which controls supply of power to the heating unit to turn it on and off;
the provision of such a heating unit in which the thermal sensing element which, in one embodiment, is located within the heat unit, either on-center or off-center, to sense heating unit temperature;
the provision of such a heating unit in which the thermal sensing element, in another embodiment, extends inwardly into the heating unit from the side of the unit; and,
the provision of such a heating unit for use in an advanced cooking unit in which the heating unit temperature is precisely controlled throughout a cooking cycle to better assist in the preparation of food.
In accordance with the invention, generally stated, an improved heating unit is used in a cooktop in which operation of the heating unit being effected by a controller. An electric current is supplied to a composition heating element to generate heat. The heating element is installed in a pan located beneath the cooktop. A thermal sensor senses the temperature of the heating element and supplies an indication of the heating element temperature to the controller which changes the amount of power supplied to the heating element as a function of the sensed temperature. Other objects and features will be in part apparent and in part pointed out hereinafter.